1. Field of the Invention
The present invention relates to a process and an apparatus for synthesizing inorganic metal oxide nanopowders and metal nanoparticles (colloid). The nanoparticles can be used as precursors to prepare nanocatalysts and nanomaterials.
2. Description of Related Art
Nanoparticle is accumulation or cluster of atoms about 1 to 100 nm length and increasingly important material used in various areas ranging from nano-technology, non-line optics, diode laser, smart sensor, information store, gene sequencing to catalysis. During the past decades, a lot of methods have been developed for preparing nanoparticles. For example, Microwave/sonication-assisted Coprecipitation, Sol-Gel Process, Hydrothermal/Solvothermal methods, Templated Syntheses, Revise Microemulsion, Hydrolyzation, and Spray Pyrolysis have been used to synthesize metal oxide nanopowders; Vapor Deposition, Mechanical Attrition, Laser Ablation, Electrochemical Reduction, Radiolysis Reduction, Chemical reduction, and Alcohol Reduction have been employed to prepare metal nanoparticles. However, some methods mentioned above require very expensive equipments, some of them lack the ability in the precise control in the generation and growth of nanocrystals, resulting in the wide distribution of nanoparticle size. In addition, some chemical methods often involve reduction of the relevant metal salts or decomposition of organometallic precursor in the presence of a suitable surfactant that is expensive.
In order to control precisely the generation rate and growth of nanocrystal for preparing nanoparticles with narrow size distribution, several new apparatuses and processes have been developed recently for the synthesis of nanoparticles, especially for the synthesis of metal nanoparticle.
Microfluidic system has been proven to be an idea medium for nanoparticles production because both mass and thermal transfer are rapid and then the nucleation of solute molecules and growth of nanocrystal can be precisely controlled (Nature, 442, 27 Jul. 2006). Wagner used microchannel reactor to generate Au nanoparticles with the size of 11.7 nm±0.9 nm (Chemical Engineering Journal 101 (2004) 251-260). Although microfluidic method can be used to produce nanoparticles with narrow size distribution and get great attention, it is insurmountable difficult to use it to prepare metal nanoparticles in large-scale.
In summary, the available methods of preparing inorganic metal oxide and metal nanoparticles, especially for metal nanoparticles, are very costly and difficult to produce nanoparticles with narrow size distribution in large-scale.
Accordingly, there remains a great need for fabricating methods of inorganic metal oxide nanopowders and metal nanoparticles with narrow size distribution. There also remains a need for methods to control growth of inorganic metal oxide nanopowders and metal nanoparticles in the process of mass-production.